The present invention relates generally to minimally-invasive techniques for repairing aneurysms occurring in hollow-body biological organs and vessels, for example, the aorta and iliac arteries, and arterio-venous fistulas. More particularly, the present invention relates to methods and apparatus for repairing aneurysms and fistulas using hardening agents that exclude the weakened tissue from a flow path.
In recent years a number of minimally-invasive techniques have been developed to repair aneurysms occurring in hollow-body biological organs and vessels, for example, the aorta, using stent-graft techniques. These techniques generally seek to xe2x80x9cre-linexe2x80x9d the blood flow path through the organ, for example, by fixing a fabric material across the section of weakened tissue. The fabric is then held in place with one or more stents, which may be implanted, for example, using a balloon catheter. Such arrangements are described, for example, in Parodi U.S. Pat. No. 5,219,355 and European Application No. 0 461 791.
Such methods and apparatus are suitable for use in only a limited number of aneurysm situations, however. In particular, for such previously known methods to be effective, the portions of the organ proximal and distal to the aneurysm (i.e., the proximal neck and the distal cuff of the aneurysm) must be relatively straight to permit the stents and liner to obtain sufficient apposition on the organ or vessel walls.
Moreover, for such previously known methods to be effective, it is important that the nondilated diameter of the aorta proximal to the aneurysm be the same (within a few millimeters) of the nondilated portion of the distal cuff. Otherwise, the stent or stents selected to fasten the ends of the liner to the proximal and distal regions of the nondilated aorta may be incapable of the range of diametral expansion needed to engage both the proximal and distal regions.
If either of the above-described conditions occur, i.e., either insufficient lengths of the proximal neck and/or distal cuff, or large diametral discrepancies between those regions, there may be leakage at either or both of the proximal and distal ends of the graft. Consequently, the aneurysm may remain subjected to flow-induced pressure, with concomitant risk of rupture. These drawbacks of previously known minimally-invasive stent graft techniques are described by T. Chuter et al. in Endoluminal Vascular Prostheses, Little Brown and Co. (1995), Chapter 2 at pp. 23-33, which is incorporated herein by reference.
As further described in the foregoing text, while complicated bifurcated endovascular grafts may be used in those cases where the distal cuff is insufficiently long, use of such previously known grafts is limited to those situations where there is no aneurysm of the iliac arteries. See, for example, Chapter 4 of the foregoing text, which is incorporated herein by reference, especially at pp. 57-59 discussing patient selection criteria. Moreover, the use of bifurcated grafts, while increasing the number of candidates for minimally-invasive procedures, raises additional issues of graft sizing.
In addition to the restriction of previously known methods and apparatus mostly to those cases where some nondilated length of the aorta and/or distal cuff remains, the occurrence of aneurysms in organs and vessels other than the aorta, for example, in the iliac arteries, is untreatable using previously known minimally-invasive techniques.
While certain techniques have been recently developed for defining a cavity within an aneurysm and then filling the cavity with a heat activated molding material, as described, for example, in International Application PCT/US94/09837, these techniques do not provide for continuity of the flow path during the treatment period. Techniques such as described in the foregoing International Application therefore do not appear suitable for use in vascular aneurysms or in other applications where the flow path must remain uninterrupted.
In view of the foregoing, it would be desirable to provide minimally-invasive methods and apparatus suitable for repairing aneurysms that can be used in patients having relatively short lengths of nondilated aorta above the aneurysm, with little or no distal cuff length.
It further would be desirable to provide minimally-invasive methods and apparatus suitable for repairing aneurysms having large changes in diameter in the nondilated aorta regions proximal and distal to the aneurysm.
It also would be desirable to provide minimally-invasive methods and apparatus suitable for repairing aneurysms in hollow-body organs and vessels other than the aorta, for example, in the iliac arteries, and for repairing arterio-venous fistulas.
It would be yet further desirable to provide minimally-invasive methods and apparatus suitable for treating aneurysms in hollow-body organs and vessels so as to exclude the aneurysm entirely from either the hemodynamic circuit in the vascular system or other biological fluids or materials flowing through hollow-body organs of a nonvascular nature, so as to prevent leakage flow to the weakened aneurysm tissue, and thereby reduce the risk of rupture.
In view of the foregoing, it is an object of this invention to provide minimally-invasive methods and apparatus suitable for repairing aneurysms in hollow-body organs and vessels defining a flow path that can be used in patients having relatively short lengths of nondilated organ above the aneurysm neck, and little or no distal cuff length, while retaining continuity of the flow path.
It is a further object of the present invention to provide minimally invasive methods and apparatus suitable for repairing aneurysms in hollow-body organs and vessels having large changes in diameter in the nondilated organ or vessel regions proximal and distal to the aneurysm.
It is another object of this invention to provide minimally-invasive methods and apparatus suitable for repairing aneurysms in hollow-body organs and vessels other than the aorta, for example, in the iliac arteries, and for repairing arterio-venous fistulas. The methods and apparatus of the present invention also find applicability in gastro-intestinal, respiratory, reproductive organ, urethral applications and elsewhere where it is desirable to xe2x80x9crelinexe2x80x9d a hollow-body organ and vessels.
It is yet another object of this invention to provide minimally-invasive methods and apparatus suitable for treating aneurysms in hollow-body organs and vessels so as to exclude the aneurysm entirely from, for example, the hemodynamic circuit, so as to prevent leakage flow to the weakened aneurysm tissue, and thereby reduce the risk of rupture.
These and other objects of the invention are accomplished in accordance with the principles of the invention by providing methods and apparatus for temporarily excluding an aneurysm from a flow path, for example, the blood flow path in the vascular system, while maintaining continuity of the flow path. A substance, such as a molding material or a hardening agent, is then injected into the aneurysm cavity. The injected substance causes, for example, thrombosis of the blood located within the cavity, or solidifies in response to exposure to an aqueous solution (e.g., blood) present in the cavity or in response to the application of heat.
In accordance with the invention, a hollow balloon catheter, structure or other means of temporarily excluding flow from the aneurysm cavity, while providing uninterrupted flow through a main lumen, is transluminally disposed within the aneurysm so that its proximal and distal ends extend past the aneurysm. The balloon catheter structure is dimensioned to isolate the aneurysm cavity from the blood flow path, while permitting blood flow to pass through a lumen in the structure uninterrupted. A suitable molding material, for example, a hydrogel or polymer of a resorbable or permanent nature, a blood hardening agent, for example, fibrin or a tissue material, for example, collagen, is then injected into the aneurysm cavity, either by a catheter, laparoscopically, or by invasive surgical means.
Once the molding material has hardened, for example, either by inducing thrombosis of blood captured within the cavity or by body temperature activation of the injected substance itself or other means for activation of the injected substance, the balloon catheter structure is deflated and removed. The hardened mass of thrombus or polymer thus forms the new lining of the organ, and relieves the weakened tissue of the aneurysm from further fluid flow stress.
In accordance with alternative embodiments of the present invention, aneurysms in the iliac arteries may also be treated using a combination of hollow balloon catheter and conventional catheter which are abutted against one another to form a mold for the new inner lining of the organ. That new inner liner is again formed by introducing a molding material or hardening agent into the cavity, defined by the walls of the aneurysm, the hollow balloon catheter and the conventional balloon catheter, to produce a coherent thrombosis or molded mass.
In yet further alternative embodiments, a wire mesh member may be disposed on the exterior surface of the hollow balloon catheter structure to serve as a framework for retaining the coherency of the thrombus formed by introduction of the hardening agent or molding material.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.